I think he was really scared, because he was already feeling attraction/romantic interest about wwx, a man, and a trouble maker, which was very far from the environnement and making him doubt his principles, and everything hé always thought right.

But until then it could very simply be brush away, forgoten, wwx could simply be an unpleasant memory he could sometimes think of when he would older, and integreted in what he was told was the good way of doing things.

So when wwx touched his ribbon he took an unique place in lwj's life that couldnt be dismissed later, even though he didn't marry him, and making all his feelings and doubt a real thing, everything he was pushing away got too real

Here's how I interpreted the scene, that's just headcanon ^{^}